xliv PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 
number of pitfalls which beset the reasoner upon the facts and 
theories of geology. 
One of the latest pieces of foreign intelligence which has reached 
us is the information that the Austrian geologists have, at last, 
succumbed to the weighty evidence which M. Barrande has accu- 
mulated, and have admitted the doctrine of colonies. But the ad- 
mission of the doctrine of colonies implies the further admission 
that even identity of organic remains is no proof of the synchronism 
of the deposits which contain them. 
4. The discussions touching the Hozoon, which commenced in 
1864, have abundantly justified the fourth proposition. In 1862, 
the oldest record of life was in the Cambrian rocks; but if the 
Hozoon be, as Principal Dawson and Dr. Carpenter have shown so 
much reason for believing, the remains of a living being, the dis- 
covery of its true nature carried life back to a period which, as 
Sir William Logan has observed, is as remote from that during 
which the Cambrian rocks were deposited, as the Cambrian epoch 
itself is from the tertiaries. In other words, the ascertained dura- 
tion of life upon the globe was nearly doubled at a stroke. 
5. The significance of persistent types, and of the small amount 
of change which has taken place even in those forms which can 
be shown to have been modified, becomes greater and greater in my 
eyes, the longer I occupy myself with the biology of the past. 
Consider how long a time has elapsed since the Miocene epoch. 
Yet, at that time, there is reason to believe that every important 
group in every order of the Mammalia was represented. Even the 
comparatively scanty Eocene fauna yields examples of the orders 
Chiroptera, Insectivora, Rodentia, and Perissodactyla; of Artiodac- 
tyla under both the Ruminant and the Porcine modifications ; of 
Carnivora, Cetacea, and Marsupialia. 
Or, if we go back to the older half of the Mesozoic epoch, how 
truly surprising it is to find every order of the Reptiha, except 
the Ophidia, represented; while some groups, such as the Orni- 
thoscelida and the Pterosauria, more specialized than any which now 
exist, abounded. 
There is one division of the Amphibia which offers especially 
important evidence upon this point, inasmuch as it bridges over the 
gap between the Mesozoic and the Paleozoic formations, often sup- 
posed to be of such prodigious magnitude, extending, as it does, 
from the bottom of the Carboniferous series to the top of the Trias, 
if not into the Lias. I refer to the Labyrinthodonts. As the 
address of 1862 was passing through the press, I was able to 
mention, in a note, the discovery of a large Labyrinthodont, with 
well-ossified vertebre, in the Edinburgh coal-field. Since that time 
eight or ten distinct genera of Labyrinthodonts have been discovered 
in the Carboniferous rocks of England, Scotland, and Ireland, not 
to mention the American forms described by Principal Dawson and 
Professor Cope. So that, at the present time, the Labyrinthodont 
Fauna of the Carboniferous rocks is more extensive and diversified 
than that of the Trias, while its chief types, so far as osteology 
